A human leukocyte interferon was first discovered and prepared in the form of very crude precipitates from natural source (1). Following this work was the substantial discovery that human leukocyte interferons exist as a class or family of proteins all exhibiting close homology and varying degrees of similar in kind antiviral activity. This work has been documented in several references as follows: (2, 3, 4, 5). This family of leukocyte interferons (commonly referred to in abbreviated form as HuIFN-.alpha.) has been reported to be composed of upwards of 15 or more individual species, having varying degrees of similar in kind antiviral activity. Characteristically, these human leukocyte interferon species have been identified by amino acid sequences consisting of from about 165 to 166 amino acids in their mature forms, by the underlying DNA sequence for each and by identification of glycosolation sites and reported antiviral activity in animal species. Indeed, at least one of these human leukocyte interferon proteins is enjoying success in certified human clinical studies. These interferon species have been and are being produced via recombinant DNA technology, notably employing the workhorse in this field, namely a transfected E. coli microorganism. Thus, these previous discoveries have enabled the production currently of sufficient quantities of human leukocyte interferon species via recombinant DNA technology from a transfected host system as to permit the recovery of relatively large amounts of very pure protein finding use for requisite clinical studies. These achievements have been reported in the references cited previously as well as other references forming a part of the state of the art currently.
As a result of the extensive studies that various workers have expended on the study of the human leukocyte interferon family, it was thought beyond doubt that the human leukocyte interferons that have been discovered and studied were composed within a single family of proteins sharing characteristics of homology, amino acid length and antiviral activity. Similar research attended corresponding success for animal, notably bovine, interferons (6).
A second class of human interferons is represented by the so called human fibroblast interferon (.beta.-interferon, or HuIFN-.beta.). Although extensive research into this compound has been conducted, surprisingly it is thought to be a single polypeptide or protein, in contradistinction to the leukocyte series where, as noted above, upwards of 15 or more species are thought to exist within the general definitional term of human leukocyte interferon (7).
A third class of human interferons is represented by human gamma interferon (HuIFN-.sub..gamma.) (8,9). Although human gamma interferon has been reported to exhibit the antiviral and antiproliferative properties characteristic of the human interferons in the leukocyte and fibroblast series, its properties are distinct in that, in contrast to the leukocyte and beta interferons, it is of shorter amino acid length and is pH 2 labile (10). Because of these distinctions, human gamma interferon is thought to be slated more for indications of antiproliferative activity with indications of substantial use in the treatment of cancer patients. Central and independent research has therefore attended the human gamma interferon molecule.
Inasmuch as human fibroblast interferon (HuIFN-.beta.) and human leukocyte interferons (HuIFN-.alpha.) are similar structurally (i.e. amino acid length and homologous sequence) and biologically (i.e. antiviral activity), it was thought by many researchers odd that the human leukocyte interferon would be composed of a family of multiple species whereas in the human fibroblast interferon case only one gene has so far been located, indicating evolutionary divergence and expansion to multiple genes within the leukocyte family but retention of a single distinct gene in the case of fibroblast interferon.
Because of this curiosity, the inventors of the present invention chose to search for additional HuIFN-.beta. genes. This effort was manifested by screening at low hybridization stringency a human genomic DNA library (11) utilizing a DNA probe prepared from a fragment spanning the mature coding region of the known HuIFN-.beta. gene. This research resulted in the surprising, serendipitous discovery of a novel, distinct family of human leukocyte interferons not previously known or thought to exist. This discovery of a novel, distinct family of human leukocyte interferons forms the basis of the present invention.